Variables Sampling for Process Parameter
Specifications are frequently written in terms of statistical parameters that describe the product to be inspected. This chapter focuses on variables sampling plans for the specifications. Standard statistical tests of hypotheses form the basis for the methodology of single sampling by variables for process parameters. Sample sizes are critical in acceptance sampling applications and may be determined from the appropriate power or operating characteristic (OC) curves of the test. When sample size must be kept to an absolute minimum, sequential plans also provide an excellent approach in sampling against specified process parameters. It is sometime desirable to plot the results of sampling inspection in the form of cumulative sum (CUSUM) charts. CUSUM charts and their variations offer many possibilities for the quality control engineer in acceptance quality control as well as process quality control.